Means for protecting electric circuits from excessive rises in pressure and similar disturbances.



. R. RIIDENBERG. MEANS :POE PROTECTING ELECTRIC CIRCUITS FROM EXCESSIVERISES IN PRESSURE AND SIMILAR DISTUBBA'NGES.-

ArPLIQATIoI- ILBD JULY 16, 1913 I v Patented Oct. 28, 1913. I

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.BNBURG, GERMANY, ASSIGNOR 'IO SIEMENS- BERLIN, GERMANY, A CORPORATIONOF F033 PROTECTING ELECTRIC CKEZCUITS FROM EXCESSIVE RISES IN PRESSUREAND SIMILAR DISTUIRBANCES.

Original application filed March 14,1913, Serial No. 754,314. Dividedand this application filed July 16,

Specification of Letters Patent.

1913. Serial $10,779,370.

To all whom it may concern.

Be it known that I, REINH LD Riionnnnno 'a subject of the Germ'anEmperor, and a resident of Charlottenburg, near Berlin, Germany, haveinvented certain new and useful Improvements in Means for ProtectingElectric Circuits from Excessive Rises in Pressure and SimilarDisturbances, of which the following is a specification.

This is a division of my application Serial No. 754,314, filed March14,1913.

My invention relates to apparatus for protecting electric circuits fromexcessive rises in pressure and similar disturbances. It refers inparticular to an arrangement also shown and described in a copendingapplication, Ser. No. 7 54,314, filed March 14th, 1913, from which: thepresent application has been divided.

My invention will be more fully understood by reference to, theaccompanying drawing, of which-- Figure 1 shows an arrangement withinductances in series with the conductors of a line and resistances inshunt to each of said inductances, and a capacity inserted between saidconductors, Fig. 2 a duplication ofthe arrangement of the inductancesand resist ances of Fig. 1, and Fig. 3 a modification of the arrangementshown in Fig. 1.

It is well known that electrical apparatus and machinery which areconnected to transmission lines or cables of some length may beprotected from. the admission ofabnormal' voltage waves by inserting achoke coil into the line. Each voltage or current wave traveling alongthe line and representing a rapidly moving excessive or reduced voltageand compared with the normal working voltage is intended to be reflectedby such a protective choke coil and to be sent back onto the line. Inreality this protective device is limited in its'action since, on theone hand, its concentrated self-induction cannot be made as high asdesired, and on the other hand, in case; of very rapid disturbances, e.g. sudden rises in voltage which occur when switching lines andapparatus into circuit, the entire self-induction of the protectivechoke coil does not come into play but only a, port-ion thereof whichmay fall as low as the leakage induction between two adjacent-turns.

Another known protective device consists of a concentrated capacitywhich is connected shortly in front of the machine or another apparatusto be protected, between the conductors or between line and ground. Inthis arrangement any disturbing wave is also reflected at the terminalsof the condenser, so that only a small portion of the disturbance,depending on the size of the condenser, can enter the machine. Perfectprotection of the winding of the machine is, however, not afforded bythis system.

The prrtective choke coil and the protective condenser have the commondrawback that, although it is true that without appreciably influencingthe low frequency working current they to a certain extent keep awayfrom the machine all disturbances in voltage lasting a very short time,they nevertheless refiect'this energy of the dis; curbing wave back ontothe line without weakening it. The disturbing waves bein thuscontinually reflected therefore travel to and fro on the line until theyare finally dissipated owing to the very low resistance of the line.Each reflection by'a device for keeping back these waves is, as alreadystated, not perfect, but such a device allows a portion of thedisturbance to pass on, whereby the windings of the electrical machineare continually abnormally strained until the disturbing wave iscompletely dissipated. I

In order to annihilate the energy of the disturbing wave it hasheretofore been proposed to employ a concentrated inductance having aresistance in shunt thereto, this combination being inserted into theline. This arrangement also has no material in fiuence upon the lowperiodicity working current, because this current can flow through theinductance having a very small resistance for low frequency. In order tobe able with this last described protective device to absorb the energyof the disturbing wave as efiectively as possible the ohmic resistancein parallel with the inrotection a ainst owerful ducts-nee must be givena value of half the line characteristic, which may be proventheoretically and experimentally. In this case the characteristic is thesquare root of the quotient of self-induction and capacity per unitlength of the lines. Half the en ergy is then converted into Joulesheat, one quarter of the energy of the incoming wave isrefiected; andthe last quarter travels past the protective device into the s'econdsection of the line. It will therefore be readily understood from theabove that these arrangements do not afford efiective disturbing waves,sinceboth the reflected disturbing wave as well as that which passesthrough have half the current and voltage amplitudes of the originalwave. In order that the wave which passes through to machinery orapparatus may be smaller, the value of the ohmic resistance must beconsiderably changed, but thereby the advantage of rapid absorption ofenergy would he lost, the effect in this case again approaching that ofa simple protective choke coil which is inserted between the conductors.

A primary object of my invention is to obviate the above defects, and topro 'ide protective means which will perfectly absorb' the incomingdisturbing wave and convert its energy into Joules heat. The incomingwave can then neither be reflected nor'pass through .the protectiyemeans to the line beyond. For providing an arrangement of this kind itis not suiiicient to employ only inductance and resistance inparalleltherewith, but it is necessary that the three elements:concentrated selfinduction, concentrated capacity, and an ohmicresistance adjusted to the characteristic of the line be simultaneouslyconnect ed at adjacent points on the line.

It is obvious that the protective device must comprise ohmic resistancefor annihilating the energy of abnormal waves of any form. Accordingly,the term ohmic resistance as used in this specification is to beunderstood as including any device in which energy is dissipated orconverted into another form of energy. That selfinduction andJcapacity'must be ccnjointly employed canbecxplainediby the fact that aconcentrated inductance reflects any incoming rapid voltage wavesubstantially with the same sign, but that a concentrated capacity sendsback the voltage wave onto the line substantially with a reversed sign.If 'itr is desired to effect the extinction of the reflected wave, thiscan therefore be brou ht about c-nly by the conjoint action infusef-induction andcapacity, whose indiuidual reflected waves neutralizeeach another. When by suitably proporticning the resistance prevision ismade for complete absorption of the incoming disturbing dil'lering fromthat of Fig. .l

waves, the protective device. will allow no energy to pass through it.Theoretically it follows that in this ideal case the ohmic resistancemust be about equal to the characteristic of the loop of line to beprotect ed almost independently of the particular construction of theprotective device.

A very cfifective protective means according to my invention is shown inFig. 1. In a line leading for instance to a machine to be protected areinserted concentrated inductances a, 8 in each side Z of the line,

while behind these a condenser k is connected between the sides Z, Z.The resistances 9, r are connected inparallel to the inductances. Thenormal working current is not materially influenced by the protectiveapparatus, but flows through the inductances s, s and passes by thecapacity in. Any rapid disturbing wavev arriving over a side Z, however,cannot enter the induc tances s, s, but will find a path through theresistance T. It is reflected at the con denser Iss0 that it must againpass through the resistance. If the value of the selfinduction andcapacity were infinite the energy of the disturbing wave would hecompletely annihilated in the resistance.

Since, however, both values must he made definite there will be slightdivergencies from the ideal case, but as theory shows, it is possible toemploy for each value of inductance and capacity such a value of thedamping resistances 9', that only an excee ingly small amount of theimpinging wave is allowed to pass or is reflected. This protectivedevice can he employed in the same way. as in front of apparatus at theend of electric lines, or at any other desired places, e. g. where theaerial lines are connected to insulated cables. In order to annihilatewave trains from both ends of the line, it is preferable to duplicatethe inductances and the resistance in shunt therewith. Such anarrangement is shown in The resistances 1g 1- are of course preterablygiven. different values if lines of different characteristics areconnected gether.

In Fig. 3 a. similar arrangement is shown for absorbing waves which arelikely to arrive from both ends, this arrangement in the inductances inthe principal-lines not being connccted with the junction points of thecondenser and the resistance 0:: one hand less apparatus is required, athe other hand the possibility present in the arrangement shown Fig. ofthe network being short circuited by the condenser in case of apuncture, is new avcid'ed, because there is alwa someresirstsnceinserien In none 0 these protective devices 1 electricoscillations can cccu: notwilhst an ing the simultan us presence cl?condensers remiss Q and inductances, because the damping re .sistance initself isof sucha value that say natural vibration is suppressed.

' erable' to connect several of the described-- protective-devices'in'series in order to dissipate with certainty that remnant of the Waveswhich passes through one protective device, onaccount of thecariacityand self-- induction having definite values. f

v the capacity. It is not absolutely necessary Theresistances employedfor annihilating the disturbing Waves are preferably made of material ofhi h specific resistance so that they may be 0 short length and may yoperate as concentrated ohmic resistances. 'lhe terms concentrated, selfinduction and capacity as used herein include any artificial increase inthe inductivity of the'lih'e or in that special condensers andinductance coils be connected in c rcuit. Ari effective concentratedinductance can, for example, be

produced by leadingthe current-carrying line through thin, concentricdisks of sheet iron, in which a powerful self-induction field can form.These disks may have between them an air-gap in order to reduce theeffect of varying permeability. Besides electrostatic and, electrolyticcondensers I may connect in the line, for example, short lengths ofcablewhich have a considerably higher capacity than the line to beprotected.

The above described protective device has the advantage not only ofdischarging its fu11ction,-as most of the previous protective deviceshave done, when the rises of potential are considerably above the normalvoltage of tlie'system, but also ofannihilatingany minor disturbingWaves.

\Vhen considerable rises in potential above the voltage of the systemoccur, the dielece-iejer the condensers or course considerably strainedTo pro ect it against'puncture, sparkgaps are preferably connected inthe well'lrnown manner in parallelwith" the. condensers, whichsparlegaps short cir- I cuit the condenserswhen'they are verymuchoverstrained' and so, on the one hand,protect their dielectric, but onthe other hanel, be cause oi the short circuit which acts as a condenserof infinite size, dc not afiecc the' action of the protective cleyicefor excess stance at f in "FigJL- If desired, other. dan1ping.resistances w be connected in serieswith these 'PIOtQCilVG spark-gaps esis 'flso shown in Fig; l. -Electrolytic con- 'derisers rovide inthemselves favorable conditions for discharge and therefore, 111general, need no special spark-gaps in parallel with them. r l'clsimz lI circuit the combination with a line oneside of the circuit, of aconcentr c ed inductance, and a resistance in -par llel inserted in theline, and a concentrated cageacityv connected between said lineanclth'e. other side oi the circuit voltages. Such spark gap is shownfor in- 2. in an wfile bilc circuit comprising the.

two sides of the line, the combination with said two sides, of aconcentrated nductance and a resis co in parallel inserted lnone side ofthe nne, and a concentrated capacity I connected'between the two saidsides,

in an electric circuit comp-rising two sides of a line, the combinationwith said two sides, of a concentrated inductance and a resistance inparallel inserted ineeach side, and'a concentrated capacity connectedbetween points of said resistances located between the ends thereof.

In witness whereof l have hereunto set my signature in presence oftwosubscribing witnesses.

nnn noen consumes.

Witnesses: v

Heresy lineman,

Newman I-IAUIT;

Homes of this intent may be 'obt'aincfi for five. cents, c'a'lnbycaressing the Gommlssieneroi Eaten,

